Effects of docosahexaenoic acid or arachidonic acid supplementation on gene expression and contractile force of rat cardiomyocytes in primary culture

While fatty acids play essential roles in the physiology of the myocardium,conventional culture media contain little lipid.We previously revealed that rat neonatal myocardium mainly contains docosahexaenoic(DHA),linoleic(LA),and arachidonic(AA)acids as polyunsaturated fatty acids(PUFAs),and these contents in cultured cardiomyocytes derived from fetal rats were markedly lower than those in the neonatal myocardium.In this study,we first assessed the effects of supplementation of DHA,LA,or AA on the fatty acid contents and the percentage change of contractile area in primarily cultured rat cardiomyocytes.Based on this assessment,we then evaluated the effects of DHA or AA supplementation on mRNA expression and further directly measured the contractile force of cardiomyocytes with the supplementations.This study revealed that percentage change of contractile area was maximized under 20μM DHA or 50μM AA supplementation while LA supplementation did not affect this contraction index,and that a widespread upregulation tendency of the mRNA expression related to differentiation,maturity,fatty acid metabolism,and cell adhesion was seen in the cultured cardiomyocytes with supplementation of DHA or AA.In particular,upregulation of the gene expression of cellular adhesion molecules connexin43 and N-cadherin were remarkable,whereas the effects on differentiation and maturation were less pronounced.Correspondingly,the increase of the percentage change of the contractile area of cardiomyocyte clusters in culture dishes with the supplementations was significant,whereas the enhancement of the contractile force was modest.These results suggest that supplementation of DHA or AA to the fetal cardiomyocyte culture may play effective roles in preventing the de-differentiation of the cardiomyocytes in culture and that the enhancement of the contractile performance may be mainly attributed to the improvement of intercellular connection.

THE IMPROVEMENT OF INFARCTED MYOCARDIAL CONTRACTILE FORCE AFTER AUTOLOGOUS SKELETAL MUSCLE SATELLITE CELL IMPLANTATION

Objective To study the improvement of infarcted myocardial contractile force after autologous skeletal muscle satellite cell implantation via intracoronary arterial perfusion. Methods Skeletal muscle cells were harvested from gluteus max of adult mongrel dogs and the cells were cultured and expanded before being labeled with DAPI (4’, 6-diamidino-2-phenylindone). The labeled cells were then implanted into the acute myocardial infarct site via the ligated left anterior descending (LAD) coronary artery. Specimens were taken at 2nd, 4th, 8th week after myoblast implantation for histologic and contractile force evaluation, respectively. Results The satellite cells with fluorescence had been observed in the infarct site and also in papi- llary muscle with consistent oriented direction of host myocardium. A portion of the implanted cells had differen- tiated into muscle fibers. Two weeks after implantation, the myocardial contractile force showed no significant difference between the cell implant group and control group. At 4 and 8 week, the contractile force in the cell implant group was better than that in control group. Conclusion The skeletal muscle satellite cells, implanted into infarct myocardium by intracoronary arterial perfusion, could disseminate through the entire infarcted zone with myocardial regeneration and improve the contractile function of the infarcted myocardium.

Modeling cell contractility responses to acoustic tweezing cytometry

Acoustic tweezing cytometry(ATC)is a recently developed method for cell mechanics regulation.Tar-geted microbubbles,which are attached to integrins and subsequently the actin cytoskeleton,anchor,amplify and transmit the mechanical energy in an acoustic field inside the cells,eliciting prominent cy-toskeleton contractile force increases in various cell types.We propose that a mechanochemical con-version mechanism is critical for the high efficiency of ATC to activate cell contractility responses.Our models predict key experimental observations.Moreover,we study the influences of ATC parameters(ul-trasound center frequency,pulse repetition frequency,duty cycle,and acoustic pressure),cell areas,the number of ATC stimuli,and extracellular matrix rigidity on cell contractility responses to ATC.The simu-lation results suggest that it is large molecules,rather than small ions,that facilitate global responses to the local ATC stimulation,and the incorporation of visible stress fiber bundles improves the accuracy of modeling.